From: "Américo Wang" <xiyou.wangcong@gmail.com>
To: Mahesh Jagannath Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org,
"Eric W. Biederman" <ebiederm@xmission.com>,
akpm@linux-foundation.org, Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden
Date: Wed, 9 Mar 2011 20:20:46 +0800 [thread overview]
Message-ID: <20110309122046.GC16951@cr0.redhat.com> (raw)
In-Reply-To: <4D771EE6.5050404@linux.vnet.ibm.com>
On Wed, Mar 09, 2011 at 12:02:06PM +0530, Mahesh Jagannath Salgaonkar wrote:
>On 08/25/2010 06:07 AM, Eric W. Biederman wrote:
>> Anton Blanchard <anton@samba.org> writes:
>>
>>> On ppc64 the crashkernel region almost always overlaps an area of firmware.
>>> This works fine except when using the sysfs interface to reduce the kdump
>>> region. If we free the firmware area we are guaranteed to crash.
>>
>> That is ppc64 bug. firmware should not be in the reserved region. Any
>> random kernel like thing can be put in to that region at any valid
>> address and the fact that shrinking the region frees your firmware means
>> that using that region could also stomp your firmware (which I assume
>> would be a bad thing).
>The issue only happens while shrinking the region using sysfs interface.
>We already have checks in kexec for not to stomp over on the firmware
>overlap area while loading capture kernel. Currently we do a top-down
>allocation for the firmware region which means it sits at the top of the
>RMO, right in the middle of the crashdump region. We can not move the
>crashkernel region beyond firmware region because kernel needs its some
>of memory in RMO region.
The crashkernel region is specified via kernel cmdline, so why
not just drop a failure when it overlaps with RMO region?
Am I missing something?
Thanks.
_______________________________________________
kexec mailing list
kexec@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/kexec
WARNING: multiple messages have this Message-ID (diff)
From: "Américo Wang" <xiyou.wangcong@gmail.com>
To: Mahesh Jagannath Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: kexec@lists.infradead.org, linux-kernel@vger.kernel.org,
linuxppc-dev@ozlabs.org,
"Eric W. Biederman" <ebiederm@xmission.com>,
akpm@linux-foundation.org, Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden
Date: Wed, 9 Mar 2011 20:20:46 +0800 [thread overview]
Message-ID: <20110309122046.GC16951@cr0.redhat.com> (raw)
In-Reply-To: <4D771EE6.5050404@linux.vnet.ibm.com>
On Wed, Mar 09, 2011 at 12:02:06PM +0530, Mahesh Jagannath Salgaonkar wrote:
>On 08/25/2010 06:07 AM, Eric W. Biederman wrote:
>> Anton Blanchard <anton@samba.org> writes:
>>
>>> On ppc64 the crashkernel region almost always overlaps an area of firmware.
>>> This works fine except when using the sysfs interface to reduce the kdump
>>> region. If we free the firmware area we are guaranteed to crash.
>>
>> That is ppc64 bug. firmware should not be in the reserved region. Any
>> random kernel like thing can be put in to that region at any valid
>> address and the fact that shrinking the region frees your firmware means
>> that using that region could also stomp your firmware (which I assume
>> would be a bad thing).
>The issue only happens while shrinking the region using sysfs interface.
>We already have checks in kexec for not to stomp over on the firmware
>overlap area while loading capture kernel. Currently we do a top-down
>allocation for the firmware region which means it sits at the top of the
>RMO, right in the middle of the crashdump region. We can not move the
>crashkernel region beyond firmware region because kernel needs its some
>of memory in RMO region.
The crashkernel region is specified via kernel cmdline, so why
not just drop a failure when it overlaps with RMO region?
Am I missing something?
Thanks.
WARNING: multiple messages have this Message-ID (diff)
From: "Américo Wang" <xiyou.wangcong@gmail.com>
To: Mahesh Jagannath Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Anton Blanchard <anton@samba.org>,
akpm@linux-foundation.org, kexec@lists.infradead.org,
linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden
Date: Wed, 9 Mar 2011 20:20:46 +0800 [thread overview]
Message-ID: <20110309122046.GC16951@cr0.redhat.com> (raw)
In-Reply-To: <4D771EE6.5050404@linux.vnet.ibm.com>
On Wed, Mar 09, 2011 at 12:02:06PM +0530, Mahesh Jagannath Salgaonkar wrote:
>On 08/25/2010 06:07 AM, Eric W. Biederman wrote:
>> Anton Blanchard <anton@samba.org> writes:
>>
>>> On ppc64 the crashkernel region almost always overlaps an area of firmware.
>>> This works fine except when using the sysfs interface to reduce the kdump
>>> region. If we free the firmware area we are guaranteed to crash.
>>
>> That is ppc64 bug. firmware should not be in the reserved region. Any
>> random kernel like thing can be put in to that region at any valid
>> address and the fact that shrinking the region frees your firmware means
>> that using that region could also stomp your firmware (which I assume
>> would be a bad thing).
>The issue only happens while shrinking the region using sysfs interface.
>We already have checks in kexec for not to stomp over on the firmware
>overlap area while loading capture kernel. Currently we do a top-down
>allocation for the firmware region which means it sits at the top of the
>RMO, right in the middle of the crashdump region. We can not move the
>crashkernel region beyond firmware region because kernel needs its some
>of memory in RMO region.
The crashkernel region is specified via kernel cmdline, so why
not just drop a failure when it overlaps with RMO region?
Am I missing something?
Thanks.
next prev parent reply other threads:[~2011-03-09 12:21 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-25 0:22 [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden Anton Blanchard
2010-08-25 0:22 ` Anton Blanchard
2010-08-25 0:22 ` Anton Blanchard
2010-08-25 0:23 ` [PATCH 2/2] powerpc: kdump: Override crash_free_reserved_phys_range to avoid freeing RTAS Anton Blanchard
2010-08-25 0:23 ` Anton Blanchard
2010-08-25 0:23 ` Anton Blanchard
2010-08-25 0:37 ` [PATCH 1/2] kdump: Allow shrinking of kdump region to be overridden Eric W. Biederman
2010-08-25 0:37 ` Eric W. Biederman
2010-08-25 0:37 ` Eric W. Biederman
2011-03-09 6:32 ` Mahesh Jagannath Salgaonkar
2011-03-09 6:32 ` Mahesh Jagannath Salgaonkar
2011-03-09 6:32 ` Mahesh Jagannath Salgaonkar
2011-03-09 12:20 ` Américo Wang [this message]
2011-03-09 12:20 ` Américo Wang
2011-03-09 12:20 ` Américo Wang
2011-03-09 12:46 ` Anton Blanchard
2011-03-09 12:46 ` Anton Blanchard
2011-03-09 12:46 ` Anton Blanchard
2011-03-09 14:21 ` Américo Wang
2011-03-09 14:21 ` Américo Wang
2011-03-09 14:21 ` Américo Wang
2011-03-14 18:13 ` Mahesh J Salgaonkar
2011-03-14 18:13 ` Mahesh J Salgaonkar
2011-03-14 18:13 ` Mahesh J Salgaonkar
2011-03-15 7:52 ` Américo Wang
2011-03-15 7:52 ` Américo Wang
2011-03-15 7:52 ` Américo Wang
2011-03-15 16:52 ` Mahesh J Salgaonkar
2011-03-15 16:52 ` Mahesh J Salgaonkar
2011-03-15 16:52 ` Mahesh J Salgaonkar
2011-03-21 3:10 ` WANG Cong
2011-03-21 3:10 ` WANG Cong
2011-03-24 4:33 ` Benjamin Herrenschmidt
2011-03-24 4:33 ` Benjamin Herrenschmidt
2011-03-24 4:33 ` Benjamin Herrenschmidt
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